Heater construction and method of making same



Feb. 9, 1965 F. R. QUINN 3,168,804

HEATER CONSTRUCTION AND METHOD OF MAKING SAME Filed Feb. 12, 1963 Frederic R. Quinn Z-VM ATTORNEY United States Patent 3,168,804 HEATER CONSTRUCTIQN AND METHGD OF MAKING SAME Frederic R. Quinn, Red Hook, N.Y., assignor to Zyrotron Industries, lnc., Red Hook, N.Y. Filed Feb. 12, 1963, Bar. No. 257,9?1 16 Claims. (Cl. 60-23) This invention relates in general to a new article of manufacture, and to a method for making the same, and more specifically to an electric heater connected to a bimetal strip and a process of molding the electric heater to a bimetal strip to form a unitary article of manufacture which allows freedom of movement for the bimetal.

The article of manufacture and method of making the same, to be herein described, has particular application in time delay devices, over-load protectors, motor starters, fluorescent starters, overload controls, and in means for changing electrical energy to mechanical energy such as thermal motors, thermal relays, and the like. For a specific application employing an article of the type with which this invention relates, reference is made to a copending application S.N. 257,592, filed February 11, 1963. In that application the article of the type in question was employed as a valve actuator for opening and closing a valve in response to variations in temperature.

An object of this invention is a novel bimetal strip construction utilized in conjunction with an electrical heater wherein the heater is isolated from the strip.

Another object is to provide a combined bimetal strip and heater constructed and arranged so as to permit the bimetal strip to have freedom for movement.

Still another object is to provide a combined bimetal strip and heater in which the heater is hermetically sealed from moisture, water and the like in a manner which will not prohibit the freedom of movement of the bimetal strip.

Still another object is to provide a construction in which a high heat transfer is had from the heater to a relatively large surface of the bimetal.

Still another object is to provide a very efiicient means for obtaining in an article of the type to be described a large movement in the free end of the bimetal with a very small quantity of power.

Still another object is to provide a relatively simple method by which an article can be made.

Still another object is to provide for a heater actuated bimetal component and method of making the same that is relatively simple in construction, positive in operation, and relatively inexpensive to manufacture.

Other features and advantages will become more readily apparent when considered in view of the drawings and the following description in which:

FIG. 1 illustrates the article of manufacture of this invention formed as an elongated member which is adapted to be cantileverly supported at one end only.

PEG. 2 illustrates an article of manufacture of this invention in the shape of a hairpin and fixedly connected at one end when in use.

Referring to the drawing, there is shown an article of manufacture formed in accordance with this invention. According to the embodiment of FIG. 1, the article comprises an elongated strip of a bimetal element 11, which when in use is fixed at one end 11A in a suitable support 12 so that the other end 11B is free to flex when heated. The bimetal strip 11 is coated with approximately 2 mils of an insulating material 13, e.g. silicone, Drifilm or other similar coating. Drifilm is the trademark for a silicone coating produced by the Dow Chemical Company. This insulating covering is applied in three separate steps with at least twenty-four (24) hours of drying or curing time between coats or applications.

An alternate form of insulatiru the bimetal strip 11 resides in spraying the bimetal strip with either an oxide or a phosphate insulation.

An electric resistance heater 14 in the form of a coil is wound about the insulated bimetal strip 11. As shown, the heater 14 consists of a wire 14A coated with a glass insulation 14B. The thickness of the glass insulation 148 on the wire 14A is only 2 to 3 mils. Preferably the glass insulation 1413 should have the same binder as the insulation on the bimetal strip, i.e. if there is an oxide coatin on the bimetal, then there should be an oxide binder in the glass insulation 14B. If there is a silicone coating on the bimetal, then there should be a silicone binder in the glass insulation 1413.

In forming the heater 14, the insulation is baked and dried on the wire 148 for a period of 4 to 24 hours.

With the heater 14 described, and coiled about the insulated coated bimetal strip 11, the same is molded in an outer covering 15 of rubber so as to entirely enclose the heater 14. In this manner the heater 14 is entirely scaled oil from moisture, water and the like. Other rubher-like material may be employed in forming the outer covering, e.g. silicones, neoprenes, and silastic or the like, the particular material used being dependent on the temperature range and conditions to which the article is to be subjected.

In the illustrated embodiments it will be noted that both ends 11A, 11B of the bimetal element 11 extend beyond the end of the outer rubber covering 15. In FIG. 1, the bimetal element 11 of the article 15), when in use, is cantileverly supported or fixed at one end 11A so that its other end 113 is free to flex. In FIG. 2 the bimetal element 20 is formed in a hairpin shape, or formed as a reverse bend in which one end 29A is fixed in a support 21 whereas its other end ZtiB is free to hex. In this form of the invention the respective components, i.e. bimetal 26, heater 22 and their respective insulating means are similar as hereinbefore described.

From the foregoing, it will be noted that coiling the respective heater 14, 22 about the bimetal elements 11, 20 and molding the same in a resilient rubber-like outer covering allows the bimetal strips much freedom of movement.

The method of making article of manufacture comprises essentially the steps of taking a bimetal strip 11 or 20 and coating the same with several distinct coatings or layers of insulation allowing for at least 24 hours of drying or curing between applications. The respective heaters 14, 22 insulated with glass and including the same binder as the insulation on the bimetal are then wound about their respective bimetal strips, and an outer layer of rubber-like insulation is molded over the strip and the heater wound thereon.

It will be understood that the articles of FIG. 1 and FIG. 2 are substantially similar except for shape.

From the foregoing it will be apparent that the article described herein and the method of fabricating the same is relatively simple in construction, easy to manufacture, and positive in operation.

While the instant invention has been disclosed with reference to two embodiments and method, it is to be appreciated that the invention is not to be taken as limited to all of the details thereof as modifications and variations thereof may be made without departing from the spirit or scope of the invention.

What is claimed is:

1. An article of manufacture comprising a bimetal strip, a thin coating of insulation covering said strip, a resistance heater, a coating of insulation covering said heater, said coating covering said heater including a binder formed of the same material forming the coating of said strip, said coated heater being wound about said coated strip, and a resilient layer of insulation covering said Strip and heater wound thereon, so that the ends of said strip project beyond the layer of said resilient insulation.

2. The invention as defined in claim 1 wherein said heater is insulated with glass.

3. The invention as defined in claim 2 wherein the insulation covering said strip and the insulation covering said heater respectively have the same binders.

4. The invention as defined in claim 2 wherein the insulation covering said bimetal is formed of silicone.

5. The invention as defined in claim 2 wherein the coating of insulation on said bimetal strip is Drifilm.

6. The invention as defined in claim 2 wherein the bimetal strip has an oxide insulation covering the same.

7. The invention as defined in claim 2 wherein the bimetal strip has a phosphate insulation covering the same.

8. The invention as defined in claim 2 wherein said bimetal strip comprises a linear elongated member.

9. The invention as defined in claim 2 wherein said himetal strip is of hairpin shape.

10. An article of manufacture comprising an elongated birnetal strip, a coating of insulating material approximately 2 mils thick covering said strip, a resistance wire heater, said wire heater being coated with a glass insulation approximately 2 /2 mils thick, said insulated wire heater being Wound about said bimetal strip, and a layer of rubber-like insulation molded about said strip and wire heater wound thereon so that the ends of said strip project beyond the layer of molded insulation.

11. An article of manufacture comprising an elongated reversely bent bimetal strip, a layer of silicone coating of approximately 2 mils thick insulating said strip, a resistance wire heater, said wire heater being insulated with a layer of glass insulation approximately 2 /2 mils thick, said glass insulation having the same binder as the insulation on said bimetal strip, said insulated wire heater being wound about said bimetal strip, and a layer of rubber-like insulation molded about said strip and wire heater wound thereon so that the ends of said strip project beyond the layer of molded insulation. 7

12. A method of molding an electric heater to a bimetal strip comprising the steps of coating a length of bimetal strip with an insulating material in several distinct applications with a predetermined curing time between each of said applications, insulating a wire heater with a covering of glass insulation having a binder formed of the same material as that forming the coating of said strip, winding said insulated wire heater about the coated bimetal strip, and molding an outer covering of a resilient insulation over the strip and wire wound thereon.

13. A method of molding an electric heater to a birnetal strip comprising the steps of coating a length of birnetal strip with an insulating coating in three separate applications with at least 24 hours of curing time between each coat, insulating a wire heater with a covering of glass insulation, winding said insulated wire eater about the coated bimetal strip, and molding an outer covering of a resilient insulation over the strip and wi e wound thereon so that the end portion of the strip extends be yond the end of the outer covering.

14. A method of molding an electric heater to a bimetal strip comprising the steps of bending an elongated strip into a hairpin shape, coating a length of bimetal strip with an insulating material in three separate applications with at least 24 hours of curing time between each coat, insulating a wire heater with a covering of glass insulation, winding said insulated wire heater in contiguous relationship about the coated bimetal strip, and molding an outer covering of a resilient insulation over the bimetal strip and wire wound thereon so that the end portions of the bimetal strip extend beyond either end of the outer covering.

15. An article of manufacture comprising an elongated bimetal strip, a coating of insulating material covering said strip, a resistance wire heater, said wire heater being coated with a glass insulation, said insulated Wire heater eing Wound about said metal strip, and a layer of rubber like insulation molded about said strip and wire heater wound thereon so that the ends of said strip project beyond the layer of said molded insulation.

16. An article of manufacture comprising an elongated reversely bent bimetal strip, a layer of silicone coating insulating said strip, a resistance wire heater, said wire heater being insulated with a layer of glass insulation, said glass insulation having the same binder as the insulation on said bimetal strip, said insulated wire heater being wound about said bimetal strip, and a layer of rubber-like insulation molded about said strip and wire heater wound thereon so that the ends of said strip project beyond the layer of molded insulation.

Reterences Qited by the Examiner UNITED STATES PATENTS 2,280,257 4/42 Pearson 338-275 X 2,355,611 8/44 Velcy 338264 X 2,357,072 8/44 Beck et al. 338-275 X 2,660,653 11/53 Berkelhamer 338-264 X 2,703,833 3/55 Vanvor 338269 X 2,894,523 8/57 Auslander et al. 280-122 3,052,788 9/62 Peters ZOO-122.01 X

JULIUS E. WEST, Primary Examiner.

EDGAR W. GEOGHEGAN, Examiner. 

1. AN ARTICLE OF MANUFACTURE COMPRISING A BIMETAL STRIP, A THIN COATING OF INSULATION COVERING SAID STRIP, A RESISTANCE HEATER, A COATING OF INSULATION COVERING SAID HEATER, SAID COATING COVERING SAID HEATER INCLUDING A BINDER FORMED OF THE SAME MATERIAL FORMING THE COATING OF SAID STRIP, SAID COATED HEATER BEING WOUND ABOUT SAID COATED STRIP, AND A RESILIENT LAYER OF INSULATION COVERING SAID STRIP AND HEATER WOUND THEREON, SO THAT THE ENDS OF SAID STRIP PROJECT BEYOND THE LAYER OF SAID RESILIENT INSULATION. 